An approach for modeling sheet metal forming for process controller design

Varying the blank holder force during forming can lead to higher formabilit y and accuracy. and better parr consistency. Process control, using on-line adjustment of the blank holder force to follow a reference process variabl e (e.g., the punch force, the draw-in, etc.) trajectory has been applied to sheet metal forming. However, process controller design has not been thoro ughly addressed. In this paper, the essential part for systematic process c ontroller design, i.e., modeling a sheet metalforming process, will be addr essed in terms of control terminology (e.g., the process model, the model u ncertainty and the disturbance). A process model for u-channel forming, i.e ., a mathematical relationship between the blank holder force and the punch force, is presented and experimentally validated. Characterization of the model uncertainty mainly due to small variations in blank size, sheet thick ness, material properties and tooling shape due to die wear and the disturb ance which is mainly due to friction is developed. [S1087-1357(00)01304-6].